by May tree I assume you mean Hawthorn. its not too early for the berries to colour up. there is a folk lore that the heavier the crop the more likely the winter is to be harsher. but I don't think this is really true. the berries are down to successful pollination back in April/May.

Plenty of hawthorns in berry already up here and I agree with SBG quantity is down to successful pollination back in spring.

Lots of people round here still regularly quote these old sayings so maybe there's something in it! Of course if we do get a hard winter the saying is reinforced and if we don't, nobody mentions that the saying didn't work!

The Rowan trees opposite me have had their red berries for the last couple of weeks, though they're still more orange red than fully red, quite normal for this time of year. It might feel like autumn's ages away, but it isn't at all - by the time end of August comes, it's dark by 8 pm and we're already getting heavy dews overnight, a signal that the summer draws to a close, even if we get good weather in September.

And I agree that quantity of berries is entirely down to growing conditions during spring/early summer, and nothing to do with an approaching hard winter. These 'signs' don't always mean what we think - last year I recall the starlings returning early, and watched the swifts gather prior to departing about 3 weeks earlier than usual, which made me wonder about a hard winter - but it wasn't at all!